# Building a Fortran compiler in pure Fortran (Mega thread)

**URL:** <https://fortran-lang.discourse.group/t/building-a-fortran-compiler-in-pure-fortran-mega-thread/4785>\
**Category:** Language enhancement\
**Created:** [November 22, 2022, 4:20pm UTC](https://fortran-lang.discourse.group/t/building-a-fortran-compiler-in-pure-fortran-mega-thread/4785 "2022-11-22T16:20:07Z")\
**Posts on this page:** 1\
**Showing post:** 15

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**Author:** ![certik](https://yyz2.discourse-cdn.com/free1/user_avatar/fortran-lang.discourse.group/certik/32/4_2.png) [@certik](https://fortran-lang.discourse.group/u/certik)\
**Post date:** [November 25, 2022, 6:12pm UTC](https://fortran-lang.discourse.group/t/building-a-fortran-compiler-in-pure-fortran-mega-thread/4785/15 "2022-11-25T18:12:34Z")

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The runtime library is here: [lfortran/src/runtime at main · lfortran/lfortran · GitHub](https://github.com/lfortran/lfortran/tree/main/src/runtime), for now anyone is welcome to contribute there. We can make it a separate project but we would still need to ensure it remains usable with LFortran, so that we can use it. The exact interface what is implemented directly in the compiler and what is a library function might change, so you will have to work with us. See also [How to contribute to LFortran's runtime library](https://fortran-lang.discourse.group/t/how-to-contribute-to-lfortrans-runtime-library/4776), where we determined that the sqrt function should probably be moved from the library into the compiler.

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